Piston pumps are currently used in wells of all sorts. For example, oil, water, landfill leachate, petrochemical spill, tank farm recovery, pipe line spill and other types of general environmental pumps. Known piston pumps generally utilize a rigid riser pipe (e.g., steel pipe or plastic pipe), having a plurality of sections of manageable lengths, generally 10-20 feet in length. The rigid pipe is installed by repeatedly blocking and lowering the rigid riser pipe, section by section. Each successive pipe section is attached to the previous section via adhesives, or screw fittings and joints. Such an operation is very time consuming and manpower intensive. Similarly, when a down well component needs to be raised for maintenance or replacement, the installation process is reversed, whereby each section must be blocked and lifted out of the well, disconnecting each rigid pipe section as it is removed.
After the rigid riser pipe is in place down the well bore, a rigid actuating rod is inserted by section through the riser pipe in a similar manner. That is, blocking and lowering of the rigid actuating rod, section by section, is required until the full length of the actuating rod is inserted into the rigid riser pipe.
Eventually, flexible actuating rods were developed to be extended through the rigid riser pipe to the bottom of the well for driving a pump piston in the rigid riser pipe which, in turn, pumps liquid back up the rigid riser and out of the well. One example of such a flexible actuating rod-driven pump assembly is shown in U.S. Pat. No. 5,429,193, owned by the assignee of the present application, the entire subject matter of which patent is hereby incorporated by reference. The unitary flexible actuating rod disclosed there allows the piston to be installed in and removed from the riser pipe more quickly. Additionally, the flexible actuating rod occupies less space when stored.
Because the pump piston was inserted and removed through the rigid riser pipe after installation of the riser pipe, the piston was limited in outer diameter to the smallest inner diameter present in the rigid riser pipe. This, in turn, limited the maximum flow rate of this type of pump, for example, to around 5 gallons per minute with a typical one inch diameter riser pipe. This limited maximum flow rate often caused low flow velocities and thus allowed silt and sand to accumulate above the piston. This unwanted buildup, in turn, caused premature failure of the pump assembly and/or more frequent maintenance to clean the sand/silt buildups.
Additionally, prior art pump assemblies using rigid riser pipes often suffer from loose riser pipe sections within the well during installation due to incorrect or insufficient attachment between sections of the rigid riser pipe. Often, the material of the rigid riser pipe was incompatible chemically with the liquid being pumped in the desired application. Further, wrong size pipes (diameters or lengths) were often chosen for a particular application and the problem was not discovered until the pump assembly was on the job site.